Function returning Structure: How does it work?

[Michael Meissner]

In article <18222 at well.sf.ca.us> rld at well.sf.ca.us (Rick Davis) writes:

| In article <1990May28.235336.5338 at Neon.Stanford.EDU>, Dave Eisen writes:
| >
| > Of course, this
| > can lead to a great deal of copying so most of the time you're better off
| > arranging things for the function to have type STRUCT * instead.
| > 
| 
| I can't agree with this too strongly.  Passing entire structures back
| and forth is almost always a serious waste of time and stack space.
| Indeed, there are circumstances where it is necessary, (i.e communications)
| but most of the time you're much better off with the structure pointer.
| Also, some implementations of C won't even let you try.  Code portability
| alone works for me.

But a clever compiler could optimize:

	struct foo func(), var;

	var = func();

and pass the address of var (assuming it returns structures by passing
a pointer as a hidden argument), so that a temporary and a structure
copy are not required.
--
Michael Meissner	email: meissner at osf.org		phone: 617-621-8861
Open Software Foundation, 11 Cambridge Center, Cambridge, MA

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